An IEEE (Institute of Electrical and Electronics Engineers) 802.16 communication system that employs OFDM (Orthogonal Frequency Division Multiplexing)/OFDMA (Orthogonal Frequency Division Multiple Access) is proposed as a BWA (Broadband Wireless Access) system, in order to support a broadband transmission network for physical channels of the wireless communication system. The IEEE 802.16 communication system is a system that considers not only a fixed state but also a mobile state of a subscriber station, wherein the subscriber station having mobility can be referred to as mobile station (hereinafter, referred to as ‘MS’).
In a radio communication system, the MS within multi-cells or multi-sectors estimates DL channel when receiving data from a base station (hereinafter, referred to as ‘BS’), measures CINR (Carrier to Interference and Noise Ratio) of the estimated DL channel, and reports CQI (Channel Quality Information) containing the CINR to the BS. In this case, the MS estimates the DL channel by using pilot signals when receiving data from the BS, and measures the CINR of the DL channel by using the pilot signals. For example, the MS measures the CINR by using all pilots in a DL sub-frame or by using pilots located in allocation region for the MS in a DL sub-frame, and reports the CQI containing the CINR to the BS.
If the MS exactly estimates the DL channel by using the pilot signals, the CINR is exactly measured in the estimated DL channel. Thus, the MS reports the CQI containing the exact CINR to the Bs, and the scheduler of the BS faithfully performs the scheduling by using the exact CINR included in the CQI and exactly controls the scheduling.
However, in case that the MS measures the CINR by using pilots located in allocation region for the MS in a DL sub-frame, it is difficult for the MS to exactly estimate the DL channel and to exactly measure the CINR because the MS can not use sufficient pilots for channel estimation and CINR measurement. In particular, in a communication environment that channel state varies according to time, the MS performs wrong channel estimation.
Also, in case that the MS measures the CINR by using all pilots in a DL sub-frame and reports the CQI containing the measured CINR to the BS, it is difficult for the MS to exactly estimate the DL channel and to exactly measure the CINR because not all pilots are dedicated to the MS. Moreover, in a multi-cells or multi-sector environment, the burst region of the MS in DL sub-frame can be overlapped with burst regions corresponding to other MSs in cells or sectors adjacent to the MS or interfered with cells or sectors adjacent to the MS. Thus, the MS performs wrong channel estimation for the burst region owing to interferences of adjacent cells or sectors.
Therefore, the MS reports the CQI containing erroneous CINR to the BS, and the scheduler of the BS receives the CQI containing erroneous CINR. Consequently, the scheduler can not perform the scheduling faithfully owing to erroneous CINR, and the waste of resource and transmission power and the decrease of the transmission rate occur. Thus, there is a demand for new scheme that can acquire exact CINR in DL channel so as to exactly perform the scheduling and the scheduling control.